WASHINGTON — Since the terrorist attacks of Sept. 11, 2001, politicians have periodically announced with fanfare that they would introduce a bill to strip the citizenship of Americans accused of terrorism. The idea tends to attract brief attention, but fades away, in part because the Supreme Court long ago ruled that the Constitution does not permit the government to take a person’s citizenship against his or her will.

But on Tuesday, President-elect Donald J. Trump revived the idea and took it much further than the extreme case of a suspected terrorist. He proposed that Americans who protest government policies by burning the flag could lose their citizenship — meaning, among other things, their right to vote — as punishment.

Even if Mr. Trump were to persuade Congress to enact a criminal statute, a dramatic shift in the balance between government power and individual freedom, anyone convicted and sentenced could point to clear Supreme Court precedents to make the case for a constitutional violation.

The obstacles include the precedent that the Constitution does not allow the government to expatriate Americans against their will, through a landmark 1967 case, Afroyim v. Rusk. They also include a 1989 decision, Texas v. Johnson, in which the court struck down criminal laws banning flag burning, ruling that the act was a form of political expression protected by the First Amendment.

David D. Cole, a Georgetown University law professor who co-wrote the Supreme Court briefs in the flag-burning case and who is about to become national legal director at the American Civil Liberties Union, said he wondered if Mr. Trump’s strategy was to goad people into burning flags in order to “marginalize” the protests against him. But he also called Mr. Trump’s proposal “beyond the pale.”

“To me it is deeply troubling that the person who is going to become the most powerful government official in the United States doesn’t understand the first thing about the First Amendment — which is you can’t punish people for expressing dissent — and also doesn’t seem to understand that citizenship is a constitutional right that cannot be taken away, period, under any circumstances,” he said.

The 1967 case involving the stripping of citizenship traces back to a 1940 law that automatically revoked the citizenship of Americans who took actions like voting in a foreign country’s election or joining its military.

The case centered on a man who had been born in Poland, became a naturalized American citizen, and later went to Israel and voted in an election there. When he subsequently tried to renew his American passport, the State Department refused, saying he was no longer an American citizen, and he sued.

In a 5-to-4 ruling, the Supreme Court called citizenship and the rights that stem from it “no light trifle to be jeopardized any moment” by politicians’ attempts to curtail it. The court said that the 14th Amendment, which guarantees due process of law, does not empower the government to “rob” someone’s citizenship. Americans, the ruling explained, can only lose their citizenship by voluntarily renouncing it.

“The very nature of our free government makes it completely incongruous to have a rule of law under which a group of citizens temporarily in office can deprive another group of citizens of their citizenship,” Justice Hugo L. Black wrote.

In a case in 1980, Vance v. Terrazas, the Supreme Court extended that precedent by a vote of 6 to 3. That case concerned a man who was born with both American and Mexican citizenship, and who as a student took an oath of allegiance to Mexico, renouncing his American citizenship in order to obtain a Mexican citizenship document.

When the State Department said he had thus surrendered his American citizenship, he sued. The court majority said he was still a citizen because the government had to prove that he specifically intended to relinquish it, rather than having said those words with a different motivation, like fulfilling his desire to obtain the certificate.

The 1989 flag-burning case was also decided by a vote of 5 to 4. It centered on a protester who had burned a flag outside the 1984 Republican National Convention in Dallas as part of a political demonstration against Reagan administration policies. The protester, Gregory Johnson, was charged under a state law that criminalized desecrating the flag and appealed his conviction.

The majority ruled that Mr. Johnson’s act was symbolic speech protected by the Constitution, effectively striking down state laws against flag desecration across the country. In response, Congress swiftly enacted a federal law against such desecration, but in 1990 the same five-justice majority struck it down, too.

Just one of the justices who participated in the flag-burning cases, Justice Anthony M. Kennedy, is still on the court today; he sided with the majority that struck down the bans. Justice Antonin Scalia, who died in February and whose seat Mr. Trump will get to fill because Republican senators refused to hold a hearing for President Obama’s nominee for the vacancy, was also in the majority.

After the 1989 decision, supporters of a flag-burning ban tried to enact an amendment to the Constitution to make an exception to the First Amendment, but it twice fell short in the Senate.

The issue flared again a decade ago. In 2005, Hillary Clinton, a senator from New York at that time, co-sponsored the Flag Protection Act. Arguing that desecration of the symbol “may amount to fighting words or a direct threat to the physical and emotional well-being” of onlookers, the bill would have banned flag burning if abusing the symbol was “intended to incite a violent response rather than make a political statement.”

The crafters of that bill sought to frame it as a compromise and an alternative to an amendment, saying “the Bill of Rights is a guarantee of those freedoms and should not be amended in a manner that could be interpreted to restrict freedom, a course that is regularly resorted to by authoritarian governments which fear freedom and not by free and democratic nations.”

But Congress did not act on the legislation. The following year, when the Senate again tried to approve a constitutional amendment to empower Congress to ban flag desecration and it fell one vote short of the necessary two-thirds majority, Mrs. Clinton was among those who voted against that measure.